Field of the Invention
The invention belongs into the semiconductor technology field. More specifically, the invention pertains to a method of programming a semiconductor memory, having a multiplicity of fuses which are provided on a semiconductor body and can each be programmed individually through the injection of energy to break or make a conducting connection.
It is well-known to use fuses for the permanent storage of data in semiconductor storage devices and for programming the redundancy in semiconductor storage devices of this type. In the former case, the state of the fuse ("conducting" or "nonconducting") establishes a data value ("0" or "1"), while in the latter case, if there is a defective storage cell, a redundant storage cell is connected into the circuit by activating the fuse.
Fuses generally consist of, for example, polycrystalline silicon or a similar suitable material that can be fused or melted through the action of energy, by means of which a previously existing conducting connection is broken. It is, however, also conceivable to use a material which is converted by the action of energy from the nonconducting state to the conducting state, in order thus to create a conducting connection. It will nevertheless be assumed below that a previously existing conducting connection will be destroyed by the action of energy.
The action of energy may be brought about, for example, by irradiating a fuse with a laser beam, or else simply by passing a relatively heavy current through a particular fuse, in order to cause it to melt.
Contemporary fuse configurations use fuses which are arranged next to one another, for example in the form of a matrix, on the surface of the semiconductor body, or chip, of a semiconductor storage device. As the number of fuses rises, that is to say as the storage capacity of the semiconductor storage device increases, the overall effect is that the required area of the chip becomes ever greater.
In order to keep the required area as small as possible, attempts have to date been made to design the fuses as small as possible in geometric terms. However, that procedure is limited by the fact that, when the fuse is activated or programmed, i.e. for example when the fuses are illuminated with a laser beam, a minimum mutual separation of the individual fuses must be respected so that the desired fuse can deliberately and reliably be melted by the laser beam.